(1) Field of the Invention
The present invention relates to manually operated pumps for dispensing liquid from a container. More specifically, the present invention relates to a non-throttling dispensing pump of the type having a manually operated actuator.
(2) Discussion of the Prior Art
A conventional non-throttling pump for dispensing liquid from a container includes a cylinder having an inlet for receiving liquid from the container through a dip tube and a piston slidable reciprocally in the cylinder. The piston has an interior chamber having an opening at one end thereof for dispensing liquid from the chamber. A valve member is positioned in the chamber and has a dispensing valve at one end portion biased toward a position closing the opening of the piston. The valve member is movable under liquid pressure against the bias away from the opening to dispense liquid from the chamber.
Conventional non-throttling and throttling pumps have a ball-type inlet valve for opening and closing the inlet of the cylinder. Although various types of prior art inlet valves have been proposed, a typical inlet valve is a free floating ball which seats on a circular valve seat. During the dispensing stroke of manual operation of the actuator, the ball valve seats to close the chamber during the initial portion of the stroke of the actuator. Because the valve member is biased toward a position closing the dispensing opening of the piston, a chamber is defined, and the chamber decreases in volume as the actuator is pushed downwardly. As pressure builds up in the chamber, the valve member positioned in the chamber is urged downwardly under liquid pressure against its bias to dispense liquid from the chamber.
When the actuator is released and moves upwardly, the ball check valve unseats and liquid is suctioned from the dip tube into the chamber, and the pump is ready for another dispensing stroke.
An inlet valve using a ball-type check valve is disadvantageous for several reasons. During the initial portion of the actuator stroke, and prior to buildup of substantial pressure in the chamber, the check valve is held in a closed position by gravity. In instances where the pump is turned to a position other than vertical, the check valve may not seat during initial portion of the stroke of the actuator, and thus the volume of the liquid dispensed may be decreased and throughout a series of actuations the volume dispensed may be erratic. During filling of the chamber as the actuator is released and moves upwardly, the ball-type check valve tends to inhibit smooth flow of liquid up into the chamber for the next stroke.
Several prior art dispensing pumps have attempted to avoid use of a ball-type check valve. U.S. Pat. No. 4,025,046 to Boris discloses an inlet valve wherein a cylindrical sleeve slides over an elongate tubular projection. However, since the tubular projection is elongate, the cylindrical sleeve, which cooperates with this tubular projection to form a seal, permits inflow of liquid into the dispensing chamber only during a latter portion of the return stroke. The pump may be operated so that full return of the actuator is not permitted. For example, a person may use the pump by pressing the actuator downwardly for a full stroke, and then permit the actuator to rise under its bias to half of the length of its return stroke, which movement is insufficient to open the valve. The person will then push downwardly again expecting further dispensing of liquid. With the device disclosed in the Boris patent, liquid does not flow into the dispensing chamber during the initial portions of the return stroke of the actuator, and thus a person operating the pump in the manner described, will not dispense any liquid.
U.S. Pat. No. 4,212,332 to Kutik et al discloses a manually operated pump wherein the floating valve is slidable with respect to the actuator. The floating valve has a generally cylindrical configuration with inwardly bent fingers at its upper region which frictionally engage the outside of the cylindrical actuator but which permit flow of liquid between the fingers. Each of the fingers is biased to engage the actuator tightly but yield to permit the actuator to slide with respect to the valve when a tapered valve tip on the lower portion of the floating valve seats on a valve seat. With the pump disclosed in the Kutik et al patent, once the tapered tip seats on the valve seat, the liquid pressure inside the floating valve is equal to the liquid pressure on the outside of the floating valve because there are ports permitting fluid communication between both the inside and outside of the valve. Because of this pressure equilibrium, the valve disclosed in Kutik et al patent would not function in a conventional non-throttling pump, wherein a pressure differential is necessary to move the valve member.
Other U.S. patents of interest include U.S. Pat. No. 4,230,242 to Meshberg and U.S. Pat. No. 4,215,805 to Giuffredi.